Method of dyeing fabric



April 30, 1940- s. H. WILLIAMS METHOD OF DYEING FABRIC Filed Nov. 24, 1939 \HVQHTOT Sumner HWiHioms {WW A'flys.

Patented Apr.- 30, 1940 UNITED STATES METHOD OF DYEING FABRIC Sumner B. Williams, Charlotte, N. C., assignor to General Dyestull' Corporation, Charlotte, N. 0., a corporation of New York Application November 24, 1939, Serial No. 305,826

1 Claim.

This invention relates to that method of dyeing fabric which involves subjecting the fabric, after it has been treated to the dye liquor, to the action of a developer solution to set the color.

Some of the objects of the invention are to provide an improved method by which a more even color in the dyed fabric may be obtained and by which the desired color may be secured with the use of a reduced quantity of dye liquor.

One common way of dyeing fabric with dye of that character that requires the action of a developer to set the color, is first to impregnate or treat the fabric with the dye liquor, which may be doneby passing the fabric through a bath of the dye liquor or passing it between a pair of rolls, one of which operates in a bath of dye liquor, and then to subject the fabric while still wet with the dye liquor to the action of the developer. This may be done by passing the fabric while still wet with the dye liquor through a bath of the developer solution or by passing the wet fabric between a pair of rolls, one of which operates in a bath of the developer solution'.

One disadvantage inherent in the above operation is that if the fabric is still wet with the dyeliquor at the time that it is subjected to the action of the developer, some of the dye ingredients are likely to be washed out of the fabric by the developer, thereby reducing the amount of dye remaining in the fabric.

As a result, the finished fabric is likely to have a different shade or color from that which was intended, thus making it difii'cult to dye fabric to match any given shade or color.

Furthermore, because of the loss'of the dye ingredient which is thus washed out of the fabric by the developer, it becomes necessary to use an excessive amount of dye to desired depth or intensity.

produce color ofga than in other portions thereof,thereby producing an unevenly dyed fabric.

It has also been suggestedto dry the fabric after it has been treated to the dye liquor andbefore it is subjected to the action of the developer, but it has been found that with ordinary drying methods, there is apt to be more or less migration of color in the fabric during the drying operation due to the fact that the drying does not occur evenly throughout the fabric, that is across the fabric from one edge to the other, or

This is especially true in the case of cotton fabrics that are being dyed with a color which has little or no affinity to the cotton fibre.

When a fabric is dried unevenly, as for instance, when the marginal portions of a web of fabric are dried before the center portion of the web, there will exist a tendency for the dye liquor and consequently the color to migrate by capillary attraction from the wetter portions of the fabric to the dryer portions, and if the color is evenly distributed throughout the fabric as it comes from the dye liquor, and migration of color such as above referred to will produce an uneven distribution of color in the fabric, the portions of the fabric in which the drying proceeded most rapidly having an excess of color while the slower-drying portions of the fabric have a deficiency of color.

The present invention has for its principal object to provide improvements in the abovementioned method of dyeing fabric in which the fabric is subjected to a drying operation after it has been treated with the dye liquor but before it is subjected to the action of the developer, by means of which improvements the steps of impregnating the fabric with the dyestuif, drying the dyed fabric, and then subjecting the dryed dyed fabric to the action of the developer, are carried out as a continuous process, the web of fabric to be dyed being given a travelling movement which takes it first through the dye bath, thence through the dryer, and thence through the developer bath. Furthermore, by means of my present improvements, the step of drying the fabric prior to its treatment with the developer ls carried out without any appreciable migration of color in the fabric, with the result that when the dried fabric is submitted to the action of the developer, the dye ingredient has the same even distribution throughout the fabric as it had be-' fore the drying operation took place. By thus eliminating any appreciable migration of-color in the fabric after it has been treated to the dye liquor, but before it is subjected to the action of the developer, an evenly dyed fabric can be produced. v

The fact that the fabric is dry when it is passed through the bath of developer solution has the advantage that the application of the developer to the fabric does not wash the dye ingredient out of the fabric as frequently happens when the fabric is passed through the developer bath while it is still wet with the dye liquor. There is, thereforano loss of dye ingredient during the developing stage, and hence any desired shade or color in the fabric can be produced with the expenditure of a less quantity of the dye ingredient than when a considerable portion of the dye ingredient is washed out of the fabric by the developer solution. My improved method of dyeing I is of especial advantage for dyeing cotton fabrics with Algosol or Naphthol colors or other colors which have little or no affinity for cotton fibre. In drying the dyed fabric, I propose to use a vapor dryer which is constructed so as to produce the even drying of the web of fabric from one edge to 'the other as the fabric passes progressively In order to give an understanding of the in-- vention, I have illustrated diagrammatically in the drawing an apparatus by which my improved method may be carried out.

In the drawing:

Fig. 1 is a diagrammatic layout showing an apparatus for carrying out the improved method;

Fig. 2 is a fragmentary sectional view on an enlarged scale, on the line 2-2, Fig. 1;

Fig. 3 is a fragmentary sectional view on the line 3-3, Fig. 2.

In the drawing, I indicates the fabric which is being dyed, and 2 indicates generally a device for applying the dye liquor to the fabric. This device may have any suitable or usual construction, and as herein illustrated, it comprises two rolls 3 and 4 between which the fabric passes, the roll 4 operating in a bath 5 of dye liquor so that the rotation of the roll 4 as the fabric passes between the rolls will apply the dye liquor to the fabric in the proper quantity.

6 indicates an apparatus for applying the developer solution to the dyed fabric in order to set the color, and while this apparatus may also have various constructions without departing from the invention, yet I have shown it as comprising two rolls 1 and 8 between which the fabricpasses,

- the roll 8 operating in a bath 9 of the developer solution, and thus, by its rotation, applying the developer solution to the fabric.

In accordance with the present invention, the

fabric I is subjected to a drying .operation immediately after the dye has been applied thereto and immediately before it is treated with the developer solution, the said dyeing, drying and developing steps being carried out as a continuous operation, so that the web of fabric is subjected progressively to the three successive steps of the complete operation, and said drying operation is carried out in such a way that there will be no appreciable migration of color in the fabric while the moisture is being removed therefrom. Such migration of color occurs when the fabric is dried unevenly, as for instance, if during the drying operation the edges of the fabric are dried faster than the center portion thereof, or if the center portion is dried faster than the marginal portions. Under such circumstances, where an area of the fabric which is still relatively wet lies adjacent an area of the fabric which is considerably dryer, the moisture in the wetter area of the fabric will travel or migrate by capillary attraction into the dryer portion of the fabric, and such migration of the moisture will carry with it some of the dye ingredient in the fabric, thereby producing a deficiency of color in the wetter areas and a surplus of color in the dryer areas.

This migration of color is particularly noticeable in dyeing cotton fabrics with Algosol or Naphthol colors or other colors which have little or no affinity for cotton fibre. and it occurs when the moisture content of the wetter area of the fabric is considerably greater than that of the adjacent dryer area, and the extent or rate of the migration decreases as the difference in the moisture content of the fabric between the wetter and the dryer portions decreases. Hence if the drying of the fabric is so carried out that at any given point in the length of the fabric the center portion and the marginal portions of the web are dried at approximately the same rate so' that there is no appreciable difference at any time during the drying operation between the moisture content of the fabric at the center portion and at the marginal portions, then there will be no appreciable migration of color during the drying operation.

If, therefore, it be assumed that there is an even distribution of the dye ingredient in the fabric after the dye liquor has been applied thereto, then if the drying of the fabric is carried out as above set forth and without any appreciable'migration of color in the fabric, this same even distribution of the dye ingredient will exist in the fabric after it has been subjected to the drying operation, and when it is subsequently subjected to the action of the developer solution.

It is desirable that the fabric should be evenly saturated with the dye solution 5 before it is subjected to the drying operation, and to provide for this, the fabric is shown as passing over a series of so-called sky-rolls H which are located between the dye-applying apparatus 2 and the dryer. The passage of the cloth over the sky rolls provides a suitable time interval during which the dye liquor which has been applied to the cloth by the roll 4 may penetrate the cloth completely so as to be evenly distributed therein.

The dryer by which the fabric is dried evenly and without any migration of color is indicated generally at It), and I propose to employ a drying apparatus constructed somewhat on the order of the apparatus illustrated in U. 8. Patent 2,071,015, February 16, 1937. This dryer is a recirculating vapor dryer and comprises an elongated drying space i5 through which the cloth passes and which is bounded by two opposite walls l6, If, each of which is provided with nozzles IS in the form of transverse slits through which the drying medium is directed against the fabric l in sheet-like jets of high velocity. This drying space l5 and its bounding walls It and I! are located within a housing IQ of the dryer i0, and said drying space I5 is shown as having a zigzag shape, the fabric being guided in its passage through the zigzag space [5 by suitable rolls 20.

The drying medium is delivered to the nozzles I8 under the required pressure by means of two fans or blowers 2|, 22, situated at opposite ends of the housing and which produce a recirculation of the drying medium within the housing. The blower 2| delivers the drying medium into an air passage 24 beneath the zigzag drying space l5 and the blower 22 delivers drying medium into an air passage 26 above said zigzag drying space is. The drying space l5 extends the width of the fabric and both sides thereof are open to channels or air passages 3! at the sides of the housing l9 and which extend to the inlet of the blowers or fans 2!, 22.

The dryer in is equipped with suitable heaters 23 for maintainingthe drying medium at the proper temperature and is also preferably equipped with some suitable heat-controlling device (not shown) by which'the drying medium is automatically kept at the required temperature.

In operation, the fan or blower 2| delivers heated drying medium under pressure into the air-passage 24, and such drying medium is delivered through the nozzles or slots l8 in the wall i! in the form of sheet-like jets of high velocity which are directed against the fabric I. Upon striking the fabric, each sheet-like jet becomes divided into two streams which flow in opposite directions along the surface of the fabric at high velocity for short distances and which develop into whirling cyclonic currents, indicated at 32 in Fig. 3, said cyclonic currents being discharged through the open sides of the drying space l into the channels 3i which lead back to the inlet of the blower 2i. The blower or fan 22 acts in a similar way to deliver drying medium under considerable pressure into the air passage 26, from which the drying medium is delivered in high velocity sheet-like jets through the nozzles iii of the wall [6, which jets are directed toward and impinge against the fabric I. The high velocity sheet-like jets thus issuing from the nozzles ill in the wall i 6 become divided into cyclonic currents upon. striking the fabric, which flow laterally into the channels 3| at the sides of the housing through which the heated drying medium is returned again to the blower 22.

Since the drying is done by recirculating the drying medium, it'will be necessary to provide the housing with a discharge outlet through which moisture laden drying medium is dis-' charged, and also to provide the housing with an air inlet through which fresh air may be admitted. Such outlet and inlet are commonly employed in dryers in which the drying medium is recirculated, and hence it is not deemed necessary to illustrate'them herein.

As an aid in obtaining the necessary even drying of the fabric so as to prevent any migration of color during the drying operation, I propose to employ adjustable bailie members 2'! situated in the air passages 24 and 26 and designed to direct the flowing drying medium into the narrow spaces 28 so as to maintain as far as possible the proper pressure in each of the narrow spaces 28 to produce a jet of the required velocity from each of the nozzles. I

I find excellent results are secured by maintaining the drying medium in the dryer III at a temperature of between 220 F. and 320 F., depending somewhat on the character of the fabric being dried, suitable means, not shown, being employed for maintaining a uniform temperature.

The recirculating drying medium at the above temperature carries a considerable amount of superheated water vapor, which, when dyeing cotton fabric, is especially effective in securin fixation of colors that have little or no ai'flnity for cotton fibre. The use of the superheated water vapor as drying medium, together with the manner in which each high velocity jet of such drying medium is directed against the cloth and is thereby converted into the whirling clonic currents, produces a substantially even drying of the fabric from edge to edge and from back to face, thereby eliminating the undesirable irrigation of color which cameo an unevenly dyed fa c.

In carrying out the invention it is not necessary to remove all the moisture from the cloth in the dryer l0, as the object of the invention will be accomplished if 85% or 90% of the moisture is removed before the fabricis subjected to the action of the developer, for by the time the fabric has been dried to a point where it retains only or of moisture, there will be no ppreciable migration of color in the fabric. Inasmuch as the fabric is delivered from the dryer ill at a relatively high temperature, I propose to pass the fabric through a cooling device indicated generally at l2 before the fabric is delivered to the developer-applying apparatus 6. 'I'hiscooling device is shown in the form of a plurality .of rolls 33 over which the fabric is festooned, the time interval which it takes for any portion of the fabric to travel through the cooling device l2 being sufficient to allow the fabric to be cooled to thedesired point.

After the fabric is delivered from the developerapplying apparatus, it may, if desired be passed over another series of sky rolls l3 for the purpose of allowing suflicient time for the developer to penetrate through the cloth and properly perform its function to setthe color.

From the sky rolls I3 the dyed fabric will be taken to any suitable washing device where it is washed, and may then be finally dried by any suitable means.

It is to be noted that the steps of applying the dye liquor to the fabric, drying the fabric evenly so as to avoid any migration of color in the fabric during the drying operation, and then subjecting the fabric to the action of the developer, are carried out as one continuous operation, the step of drying the fabric so as to avoid any migration of color following immediately after the dyeing of the fabric, and the step of subjecting. the dried fabric. to the action of the developer following immediately after the fabric is dried.

By drying the fabric by the use of the highvelocity sheet-like jets of drying medium which, upon striking the fabric, are converted into cyclonic currents, as indicated in Fig. 3, which not only have the cyclonic form, but also flow laterally into the side spaces 3|, and maintaining the drying medium at the proper high temperature, the drying operation may be carried out evenly from edge to edge of the fabric so that there will be no wetter portions either at the center of the fabric or at the edges lying adjacent dryer portions which would result in the undesirable mi' with a gaseous medium evenly and at the same rate from edge to edge of the fabric and without any appreciable migration ofcolor in the fabric during the drying operation, and then immediately subjecting the dried dyed fabric to the action of a suitable developer to set the color.

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